Electric bell



y direction. I

Patented Mar. 21, 1944 UNITED STATES PATENT OFFICE ELECTRIC BELL Lewis J. Stern, Adrian, Mich, assignor, by mesne assignments, to Schwarze Electric Company, Chicago, 111., a limited partnership of Illinois Application October 2, 1941, Serial No. 413,268

" sufllcient force to produce a loud noise it is nec- 2 Claims.

This invention relates to electric bells and, more particularly, direct current bells.

Present-day direct current bells fall intotwo general groups. One of these groups is known as the clapper type in which a steel ball at the end of a light springy arm attached to the armature, strikes the gong, and the plunger type in which a plunger is, forced towards the gong by the armature.

The clapper type of gong consists of an electro-magnetic circuit with which is associated an armature, one end of which is pivoted or mounted on a fiat spring and the other end of which carries a springy wire at the end of which is attached a bell. In the case of th pivoted armature the spring is employed to pull the armature away from the electro-magnet. The armature itself carries a contact point so arranged that it touches another contact point mounted in an insulated flat spring member when the coils are de-energized and the armature is away from the pole faces of the electro-magnet. The electrical circuit is through the spring contact point to the contact point on the armature and from there to the electro-magnet winding, the other sideof which is connected to a power line. It is apparent that when the electro-magnet is energized with sufiicient force to pull the armature toward the pole faces the circuit through the contact on the armature and on the insulated spring will be broken, causing the armature to fall back and again complete the circuit thereby repeating the action. If g both these contacts wer rigid the stroke of the armature in the direction away from the electro-magnet would be limited which would resultin a vibration of short duration and high frequency. Owing to the fact that the one contact is mounted on a flat spring and is impelled backwards by the inertia of the armature going in that direction the length of stroke is substantially increased as the momentum of the armature and its associated spring wire and ball is suflicient to require a small amount of time for its dying out and being again built up in the opposite direction under the influence of the electro-magnet.

When the bell is in proper adjustment the action is such that the armature actually pulls against the pole faces and is brought to a sudden stop, but the momentum of the ball at the end of the wire is great enough for it to continue in the direction of the bell and strike the bell even though the armature has already reversed its In order to have the bell sui e th gong with gs essary to use sufiicient energizing force in the electro-magnet to overcome quite a strong return spring and without the use of such a spring operating a heavy armature the inertia of the moving armature system away from the pole faces would not be sumcient to maintain contact lon enough to give an adequate amplitude to the vibrating system. It should be noted here that in this type of operation the contact points close at exactly the same point on the return stroke at which they break on the forward stroke and that the so-called lost motion which is present in these :bells is one resulting entirely from the inertia of the vibrating elements.

The plunger type bell operates in substantially the same manner as the clapper type. However, in this type of bell there is always a pivoted armature which in turn strikes a metal pin of small diameter which is free to move longitudinally when struck by the armature. This pin is held away from the bell and against the armature by its own return spring but is free to move away from the armature under its own momentum after the armature comes to rest upon striking the pole faces after breaking its own contact. In this type of bell the contacts break at exactly the same point in the forward stroke that they close on the reverse stroke and the so-called lost motion present in this type of construction is also only due to the inertia of the moving parts. While this term lost motion has always been used in descriptions of direct current bells a more descriptive term would be loose coupling as the parts are free to move to some extent independently of each other but the making and the breaking of the contacts must necessarily take place at the same displacement point in the cycle of the armature.

In both the plunger and clapper types of bells heretofore described, the adjustment of the contact points is very critical owing to the fact that the armature must break the circuit at exactly the right point in the forward stroke in order to get regular operation from the bell and to insure that the plunger or clapper strikes the gong.

Accordingly, an object of the present invention is the provision of a bell of novel construction which overcomes the disadvantages of former bells by means of a novel arrangement in which the plunger must travel a predetermined distanc during each oscillation.

Another object is the provision of a novel electromechanical arrangement having a vibrat- .the bell consists of a disc shaped base plate I0,

Fig. 4, provided with a pairof spaced bosses II,

Fig. 3, each having an opening through which a stud l2 extends. The studs are each provided with a collar I3 which may be spot welded to the under side of the base, and a threaded part I4 depending therefrom. Feet I5 of bridge I6 have openings through which the studs pass, and nuts I 'I secure the bridge to the tops of the bosses.

The top of the bridge has a flattened part is having in its mid-section an opening I9 under which and in alignment therewith is secured by suitable means, a nut 20. A casing 25 having a flat axially disposed top section 25 which rests on the part I8 of the bridge is provided with a cylindrical wall portion 21 flanged at 28 to overlie the base plate, the flange being turned down at 29 to overlap the edge of the base and prevent any motion of the base and casing in respect to each other. A suitable gasket 30 may he placed between flange 28 and base plate II].

A gong 3I is concentrically secured to the cars ing by means of an eyelet 32 disposed in openings in the gong and casing members. A hollow screw 33 having a hexagonal head 34 extends through the eyelet and screws into nut to hold the flattened part of the top of the casing against the flat top part IB of the bridge and also to press the flange 26 against gasket 30 and base plate I0, so thus by a single screw the whole structure is held together. A washer 35, cut away on its under surface at 36 so as to clear the eyelet and distribute pressure is placed on the screw between the head thereof and the upper surface of the gong.

Solenoid winding 40 is supported between angle plates 4| and 42 secured to the Referring to Fig. 2, a brass tube provided with an opening 46 reduced in size at one end extends through the solenoid. The other end of the tube is closed by a hollow screw which serves as a stop for a plunger assembly consisting of a plunger 48 provided at one end with a bronze striker pin 49 which reciprocates in opening 46. Disposed on the pin between the partially closed end of the tube and shoulder 50 of the plunger is a spring 5| which tends to move the plunger toward stop screw 41. The opposite end of the plunger is turned down forming a shoulder 52 and a neck 53 which slides freely into an opening 54 of som what greater diameter in a hollow cylinder or sleeve 55 of insulating material which is of approximately the same diameter as plunger 48. A brass washer 56 is secured against a shoulder formed at the end of neck 53 by pressing or peening over the end thereof at 5?. The washer clears the surface of a cavity 58 in the sleeve, but when the solenoid is energized in the plunger will move toward the right of the drawings and when washer 56 strikes shoulder 60 it will carry the sleeve along with the plunger. Likewise when the plunger is moved toward the left by spring 5| sleeve 55 will remain stationary until shoulder 52 of the plunger strikes the end surface of the sleeve moving the sleeve to the left with the plunger.

Mounted in suitable insulating means 6| on a bracket 62, secured to angle piece 4| is a contact assembly consisting of a contact spring 63 provided with a contact point 64 which cooperates with a contact point 65 carried by contact spring 66 formed with a depending loop which extends into an opening 68 in the top of tube 45, the loop tending to rest in the path of sleeve 55 and to be engaged by the end 69 thereof. Contact spring 63 rests against stop member ID when the contacts are open.

The arrangement operates as follows: The parts in Figure 2 are shown in the position they occupy after the bell has been struck and plunger 48 has already started its return movement under the influence of spring 5|. The plunger continues its movement and shoulder 52 of the plunger engages surface of the insulating sleeve carrying it along to the left. The surface 69 engages loop 61 of contact spring 66 closing contacts and 64 which are connected to the solenoid and a source of potential (not shown) in a well known manner. Momentum carries the plunger some distance to the left, beyond the point where the contacts actually close, and loop 61 rides up upon the cylindrical surface of sleeve 55 momentarily, moving contact spring away from stop I0 and producing a wiping action between the contact points. When the magnetomotive force of the solenoid overcomes the inertia of the plunger and sleeve, the plunger starts to move again toward the right, but the contacts do not open until the plunger has travelled sufficiently far for washer 56 to engage shoulder 59 of the sleeve and with its continued motion draw the sleeve out of engagement with contact loop 61 permitting the contacts to break again. After breaking the circuit the plunger continues to move forward by momentum until it strikes the gong at which time it reverses its direction under the influence of spring 5I and the action is repeated.

An opening in base plate III is covered by a connecting block I55 of molded insulating material fastened to the base by screws and nuts I56. The block is formed to cover as well as fill the opening in the base plate. Two openings I51 are provided therein from each of which a sturdy metal bar I58 projects. The upper part of bars I58 are turned over so as to fit in recesses formed in the upper surface of the connecting block substantially parallel to the base where they are securely held by nuts I60 and bolts I6I molded into the connecting block. This arrangement provides binding posts as well as external connecting means to which the bell circuits are attached. Bars I58 and the circuits therefor are further separated and protected by an upwardly projecting part I62 of the connector block which is higher than the tops of bolts I6 I.

Bars I58 are arranged to fit into spring connecting clips held by a terminal block secured to the underside of a cover plate of novel construction adapted to fit outlet boxes of the kind in general use,

A preferred embodiment of a cover plate according to the present invention consists of a metal disc I!!! provided on its upper surface adjacent to the edge thereof with a concentric ridge IH arranged to engage the under surface of base plate Hi, the ridge being sufficiently high so that parts depending from base plate I0, particularly the ends II of studs I2 are held clear of the surface of the cover plate. A boss I12, has a nut I13 secured to the under side thereof. A screw I14 extending through hollow screw 53 and through base plate I is held by nut I13 of the cover plate. With this arrangement the bell is secured to the cover plate by a single screw. A groove I15 in the body of the screw retains a loosely fitting spring ring I18 which prevents screw I14 from being entirely withdrawn from screw 33. With this arrangement, the person installing the bell has only one part to handle.

Cover plate I18 is provided with an opening which is covered by a molded terminal block I80 secured to the under side of the plate. The opening is disposed to be in register with the corresponding opening for the terminal block I55 on base plate Ill. The molded part of terminal block I80 is identical with bell terminal block I55. Block I80, however, has a sturdy brass strip I8I secured by a nut I82 and a bolt I83 in each of two channels formed in the blocks. The brass strips are formed into U-shaped clips I84 registering with the lower ends of openings formed in the block communicating with the upper surface thereof to receive the connecting bars I58 of the bell which when inserted into the channels spread the clips which exert sumcient pressure on the bars to support the bell securely by this means alone, notwithstanding the fact that the single screw arrangement described above is -lso provided as a support.

Power wires may be attached by means of nuts I86 on bolts I83 to clips I84.

A protecting cover I81 of insulating material is pivoted to the terminal block at I88. The cover is normally held in position over terminal bolts I83 by a small retaining point I88 (shown on the corresponding part of terminal block 55, Fig. 3) formed on the terminal block which engages the edge of a hole, not shown, in cover I81. When access to the connector members is required the cover may be turned on its pivot as indicated in the drawings by dotted lines. With this arrangement cover plate I cannot be secured to the outlet box until cover I81 is restored to its normal position.

Cover plate I10 may be provided with a plurality of differently spaced hole arrangements for fastening the plate to various kinds of outlet boxes. In Fig. 3 screws I90 are shown attaching the cover plate to outlet box I9I.

The bell structure just described may be readily changed to a guarded hell by means of a disc shaped plate, not shown, of greater diameter than base plate I0 provided with a plurality of openings which clear projections depending from the under side of base plate I0 so the surfaces of the plates may be placed in uniform contact with each other. Two of the openings in the plate are disposed to receive threaded members I4 of stud I2, Fig. 3 permitting the plates to be secured to each other in concentric relation. A dome-shaped guard structure is secured to the edge of the plate, the arrangement being described in detail in applicants co-pending application Serial No. 413,267 flied October 2, 1941.

While but one embodiment of the invention has been disclosed herein, it will be understood that numerous modifications of the same may be made without departing from the spirit and scope of the invention,

What is claimed is:

l. A switch for an electric bell of the plunger type comprising a solenoid, a plunger therefor formed with concentrically disposed members of smaller cross-section projecting from opposite ends thereof, one of said members being a bell striking member, a tube in which the plunger is free to reciprocate provided at one end with a co-axially formed opening smaller in size than the bore of said tube through which opening the bell striking member reciprocates, a compression spring disposed on the last-mentioned member between said plunger and the end of said tube for returning said plunger to an initial position, a switch operating member comprising a loose fitting sleeve of insulating material disposed within said tube on the other of the members projecting from said plunger, stop means on said member limiting the relative axial movement of the plunger in respect to said insulating sleeve whereby said sleeve is loosely coupled to said plunger, an opening formed in one side of said tube overlying said sleeve when the plunger is in its initial position, a pair of co-operating contact members, tensioned so as to tend to open, adapted to be connected in a vibratin circuit for said solenoid, insulated means for supporting said contact members outside of said tube and out of contact therewith, a loop substantially U-shaped formed in one of said contact members depending through the opening in said tube and engaging the side of said sleeve when said sleeve and plunger are in their initial positions, the sleeve holding the contacts in engagement with each other whereby the operating circuit for said solenoid is closed through said contact members, the arrangement being such that if the contact members are connected in an energizing circuit for the bell, the plunger will be moved by said solenoid compressing said spring and after the plunger has moved a predetermined distance the stop mean on said member will engage said sleeve and withdraw the latter from under the depending loop of said contact spring permitting the contact springs to open thus breaking the solenoid circuit, whereupon the spring returns the plunger to its normal position and after the latter has moved a predetermined distance it engages the contact leeve carrying the latter along until the sleeve again engages the contact loop, closing the contacts and the energizing circuit for the solenoid.

2. An arrangement according to claim 1 in which said tube is threaded at one end and an adjustable stop member is screwed thereinto, said member being formed so as to engage an edge of said sleeve whereby said sleeve in turn stops said plunger in order that said plunger and sleeve will invariably rest in the same relative position whereby the plunger will always move a predetermined distance from its position of rest before engaging the sleeve.

LEWIS J. STERN. 

